Physical and morphological properties of first-year Antarctic sea ice in the spring marginal ice zone of the Atlantic-Indian sector

Johnson, Siobhan; Audh, Riesna R.; Jager, Wayne de; Matlakala, Boitumelo; Vichi, Marcello; Womack, Ashleigh; Rampai, Tokoloho

doi:10.1017/jog.2023.21

Cited by 5 publications

(10 citation statements)

References 41 publications

(82 reference statements)

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“…Similar conditions were inferred from the stratigraphy of cores collected in spring 2019 by Johnson et al. (2023).…”

Section: Discussionsupporting

confidence: 86%

“…The daily back‐trajectory (Figure 2) of the FYI floe was computed using the low‐resolution sea‐ice drift product of the EUMETSAT Ocean and Sea Ice Satellite Application Facility (OSI‐SAF; OSI SAF, 2021) and the open‐source Lagrangian tool OceanParcels (Delandmeter & Van Sebille, 2019; Johnson et al., 2023). The coarse resolution of the sea‐ice drift product limited back‐tracking near the ice edge; the trajectory was thus computed from the first location south of M03 that produced 1 month of back‐tracked locations for the floe.…”

Section: Methodsmentioning

confidence: 99%

“…All data presented here are archived at Zenodo via Audh et al (2023), Johnson et al (2022), andOmatuku Ngongo et al (2022).…”

Section: Data Availability Statementmentioning

confidence: 99%

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Rafting of Growing Antarctic Sea Ice Enhances In‐Ice Biogeochemical Activity in Winter

Audh,

Fawcett,

Johnson

et al. 2023

JGR Oceans

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The study of Antarctic first‐year sea‐ice biogeochemistry has been limited by samples mostly being collected in pack ice during summer, with few winter data available. Measurements from the Antarctic marginal ice zone (AMIZ) have proven even more difficult to obtain. The AMIZ is a broad, circumpolar feature of the Southern Ocean found at different latitudes during the year where light and nutrients are high enough to sustain primary production and influence ecosystem functioning. We present the first biogeochemical data set from growing ice collected in the Atlantic AMIZ during winter 2019, including measurements from young pancake ice (YI) and consolidated first‐year ice (FYI). Measurements of sea‐ice temperature, salinity, crystal structure, δ18O, chlorophyll, and nutrient concentrations were used to investigate the winter sea‐ice habitat and decipher the conditions under which the ice formed and grew. Model simulations support the hypothesis that nutrient accumulation in advancing sea ice cannot be explained by passive seawater entrainment and thermodynamics alone. Our data confirm that winter sea ice is biogeochemically active and accumulates remineralized nutrients. We further propose that mechanical thickening enhances the reservoir of nutrients during the ice growth season. The biogeochemical transition from YI to FYI does not appear to be a linear progression of thickness with habitat space reduction as sea ice consolidates. Instead, FYI bulk biogeochemistry results from multiple cycles of rafting of YI, which conserves the biogeochemical properties of YI in the FYI, ultimately increasing the overall nutrient and chlorophyll content.

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“…Similar conditions were inferred from the stratigraphy of cores collected in spring 2019 by Johnson et al. (2023).…”

Section: Discussionsupporting

confidence: 86%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Rafting of Growing Antarctic Sea Ice Enhances In‐Ice Biogeochemical Activity in Winter

Audh,

Fawcett,

Johnson

et al. 2023

JGR Oceans

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“…Grease ice between floes was not observed. Structural analysis of ice cores from a similar region to the SWIFT buoy deployments shows that the sea ice was composed of a more columnar crystal structure (Johnson et al, 2023). This difference in crystal structure can be reflected in the strength and elasticity of the sea ice floes (Skatulla et al, 2022), possibly impacting how they respond to the wave field.…”

Section: Tablementioning

confidence: 98%

Direct Observations of Wave‐Sea Ice Interactions in the Antarctic Marginal Ice Zone

Wahlgren,

Thomson,

Biddle

et al. 2023

JGR Oceans

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Wave energy propagating into the Antarctic marginal ice zone effects the quality and extent of the sea ice, and wave propagation is therefore an important factor for understanding and predicting changes in sea ice cover. Wave‐sea ice interactions are notoriously hard to model and in‐situ observations of wave activity in the Antarctic marginal ice zone are scarce, due to the extreme conditions of the region. Here, we provide new in‐situ data from two drifting Surface Wave Instrument Float with Tracking (SWIFT) buoys deployed in the Weddell Sea in the austral winter and spring of 2019. The buoy location ranges from open water to more than 200 km into the sea ice. We estimate the attenuation of swell with wave periods 8‐18 s, and find an attenuation coefficient α = 4 ⋅ 10−6 to 7 ⋅ 10−5 m−1 in spring, and approximately five‐fold larger in winter. The attenuation coefficients show a power law frequency dependence, with power coefficient close to literature. The in‐situ data also shows a change in wave direction, where wave direction tends to be more perpendicular to the ice edge in sea ice compared to open water. A possible explanation for this might be a change in the dispersion relation caused by sea ice. These observations can help shed further light on the influence of sea ice on waves propagating into marginal ice zones, aiding development of coupled wave‐sea ice models.

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“…These were acquired underway from the automatic met-station, which was operated by the South African Weather Service (Ryan-Keogh & Vichi, 2022). Furthermore, sea ice temperature in the MIZ was retrieved from cores extracted at four stations along the southward route (Audh et al, 2022;S. Johnson et al, 2023;Omatuku Ngongo et al, 2022;Skatulla et al, 2022): two during the winter expedition and two during the spring campaign.…”

Section: Field Measurementsmentioning

confidence: 99%

High‐Resolution Thermal Imaging in the Antarctic Marginal Ice Zone: Skin Temperature Heterogeneity and Effects on Heat Fluxes

Tersigni,

Alberello,

Messori

et al. 2023

Earth and Space Science

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Insufficient in situ observations from the Antarctic marginal ice zone (MIZ) limit our understanding and description of relevant mechanical and thermodynamic processes that regulate the seasonal sea ice cycle. Here we present high‐resolution thermal images of the ocean surface and complementary measurements of atmospheric variables that were acquired underway during one austral winter and one austral spring expedition in the Atlantic and Indian sectors of the Southern Ocean. Skin temperature data and ice cover images were used to estimate the partitioning of the heterogeneous surface and calculate the heat fluxes to compare with ERA5 reanalyses. The winter MIZ was composed of different but relatively regularly distributed sea ice types with sharp thermal gradients. The surface‐weighted skin temperature compared well with the reanalyses due to a compensation of errors between the sea ice fraction and the ice floe temperature. These uncertainties determine the dominant source of inaccuracy for heat fluxes as computed from observed variables. In spring, the sea ice type distribution was more irregular, with alternation of sea ice cover and large open water fractions even 400 km from the ice edge. The skin temperature distribution was more homogeneous and did not produce substantial uncertainties in heat fluxes. The discrepancies relative to reanalysis data are however larger than in winter and are attributed to biases in the atmospheric variables, with the downward solar radiation being the most critical.

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Physical and morphological properties of first-year Antarctic sea ice in the spring marginal ice zone of the Atlantic-Indian sector

Cited by 5 publications

References 41 publications

Rafting of Growing Antarctic Sea Ice Enhances In‐Ice Biogeochemical Activity in Winter

Rafting of Growing Antarctic Sea Ice Enhances In‐Ice Biogeochemical Activity in Winter

Direct Observations of Wave‐Sea Ice Interactions in the Antarctic Marginal Ice Zone

High‐Resolution Thermal Imaging in the Antarctic Marginal Ice Zone: Skin Temperature Heterogeneity and Effects on Heat Fluxes

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